WO2023042215A1

WO2023042215A1 - Brushless motor and cooling system thereof

Info

Publication number: WO2023042215A1
Application number: PCT/IN2022/050814
Authority: WO
Inventors: Jaydeep VIRAMGAMA; Milan Hansaliya
Original assignee: Viramgama Jaydeep; Milan Hansaliya
Priority date: 2021-09-14
Filing date: 2022-09-13
Publication date: 2023-03-23

Abstract

The present invention discloses a cooling system (4) for outrunner brushless DC motor (1) which includes a radial heat transfer element (41) having a plurality of fins (413) on its outer surface where the radial heat transfer element (41) is fitted in the stator core (21) to extract heat from the stator (2). The heat from the radial heat transfer element (41) is removed by a plurality of heat pipes (42) and the plurality of heat pipes (42) is further cooled by a coolant (433) flowing in the hollow stator shaft (433) of the stator (2). The cooling system (7) for inrunner brushless DC motor (6) consists of a heat transfer element (71) which has a plurality of fins (713) on the inner surface and encloses the stator (61). A plurality of heat pipes (72) and a fan (73) are provided to cool the heat transfer element (71).

Description

TITLE: Brushless Motor and Cooling System Thereof

FIELD OF THE INVENTION

The present invention generally relates to the field of cooling system for motors, even more particularly, forced fluid cooling system for brushless type motors.

BACKGROUND OF THE INVENTION

This section is intended to provide information relating to the field and background of the invention and thus any approach/functionality described below should not be assumed to be qualified as prior art merely by its inclusion in this section.

Climatic variation, energy and environmental problem are common problems always faced by all of people in the society. Some countries aggressively implement the strategy of energy saving and environment protection, the world has entered a new era for solving the common problems always faced by all of people in the society. Greenhouse gas emission, energy consumption and exhaust gas emission are the top three issues in the traffic and transportation field, the effective solution of which directly affects whether the common problems faced by all of people can be solved effectively.

The vehicles that allow people to move from one location to another have been used since the dawn of time. Internal combustion engines power these vehicles. Due to increased cars, IC engines create environmental pollution by emitting greenhouse gases, and fossil fuels are eliminated. About the newest developments in the automobile industry, new techniques are assisting in improving fuel economy and reducing pollutants. Another technical development is Hybrid cars, which utilize both IC engines and electric motors to propel the vehicle or automobile. In i the future, clean and green energy will be generated with zero emissions. The majority of current industry interest in designing and manufacturing electric vehicles has been driven by the design and manufacturing of electric vehicles. Budget constraints, short distance travel, and long charging time are the main problems for vehicles that run on batteries. Consumers are always on the lookout for improved travel solutions.

A typical brushless motor has permanent magnets that rotate around a fixed armature, eliminating problems associated with connecting current to the moving armature. An electronic controller replaces the commutator assembly of the brushed DC motor, which continually switches the phase to the windings to keep the motor turning. The controllers used maybe MOSFET or IGBT and ESC. The controller performs similar timed power distribution by using a solid-state circuit rather than the commutator system. Brushless motor commutation can be implemented in software using a microcontroller, or may alternatively be implemented using analog or digital circuits. Because the controller implements the traditional brushes' functionality it needs to know the rotor's orientation relative to the stator coils. Some designs use Hall Effect sensors or a rotary encoder to directly measure the rotor's position. Others measure the back-EMF in the undriven coils to infer the rotor position, eliminating the need for separate Hall Effect sensors. These are therefore often called sensorless controllers. the permanent magnets are part of the rotor. Three stator windings surround the rotor. In the outrunner (or external-rotor) configuration which is also called hub motor, the radial-relationship between the coils and magnets is reversed; the stator coils form the center (core) of the motor, while the permanent magnets spin within an overhanging rotor which surrounds the core. The flat or axial flux type, used where there are space or shape limitations, uses stator and rotor plates, mounted face to face. Outrunners typically have more poles, set up in triplets to maintain the three groups of windings, and have a higher torque at low RPMs. In all brushless motors, the coils are stationary.

There are two common electrical winding configurations for brushless DC motors; the delta configuration connects three windings to each other in a triangle-like circuit, and power is applied at each of the connections. The Wye (Y-shaped) configuration, sometimes called a star winding, connects all of the windings to a central point, and power is applied to the remaining end of each winding. A motor with windings in delta configuration gives low torque at low speed but can give higher top speed. Wye configuration gives high torque at low speed, but not as high top speed. Although efficiency is greatly affected by the motor's construction, the Wye winding is normally more efficient. In delta-connected windings, half voltage is applied across the windings adjacent to the driven lead (compared to the winding directly between the driven leads), increasing resistive losses. In addition, windings can allow high-frequency parasitic electrical currents to circulate entirely within the motor. A Wye-connected winding does not contain a closed loop in which parasitic currents can flow, preventing such losses.

The brushless motors offer several advantages over brushed DC motors, including high torque to weight ratio, increased efficiency producing more torque per watt, increased reliability, reduced noise, longer lifetime by eliminating brush and commutator erosion, elimination of ionizing sparks from the commutator, and an overall reduction of electromagnetic interference (EMI).

The maximum power that can be applied to a brushless motor is limited almost exclusively by heat, because too much heat weakens the magnets and will damage the windings' insulation. This also affects the working efficiency and the working life of the motor. To address these issues different methods of cooling were proposed to remove the heat from the motor.

In the US application US20060017335A1 the invention is motor having a stator, a rotor and a sealed housing enclosing the stator and rotor. The stator is mounted to the housing and the rotor is mounted to a shaft journaled to the housing for rotation about a longitudinal axis. The stator defines a cavity longitudinally adjacent the stator and rotor. The motor has a plurality of sealed pipes, each sealed pipe has a coolant medium contained in it, where one closed end of the pipe is located within the cavity and another closed end of the pipe is located external to the housing. The sealed pipes used are heat pipes, where the heat pipes are aligned substantially in the longitudinal direction and connected in common with a heat exchange fin at the external end. In this invention the cooling is done by heat pipes which are partially extended outside the motor body where the cooling ends of the heat pipes have fins.

The patent US7569955B2 discloses an electric motor including a motor portion, a cooling portion and a plurality of heat pipes. The motor portion includes a stator and a rotor that when energized with electric current causes the rotor to rotate. The motor portion comprises a motor frame that encloses the rotor and stator from exterior elements. The cooling portion is adjacent to the motor portion and exterior of the motor portion. In various embodiments it defines a fluid chamber containing a quantity of fluid that is prevented from contacting interior of the motor portion. The plurality of heat pipes within the motor portion extend from the motor portion to the cooling portion such that the fluid contacts the heat pipe within the cooling portion in order to remove heat from the heat pipe. In this invention the heat from the motor is removed by heat pipes and the cold end of the heat pipes are present in the fluid chamber which cools the heat pipes. In the patent US9331552B2 the invention is an electric motor cooling system which is provided with heat pipes where heat is captured within at least one hollow region within the motor's rotor shaft. An end of the heat pipe that extends out and away from the end of the rotor shaft is coupled to a heat exchanger, for example a heat sink in which the fins of the heat sink are shaped as fan blades. During motor operation, as the rotor heats up thermal energy is absorbed by the heat pipe within the rotor shaft and transferred to the heat sink for efficient removal. In this invention the heat is removed by heat pipes which are fitted in the rotor shaft and the cold end of the heat pipes are cooled by fins or coolant flow.

The patent CN106452013B discloses an axial flux hub motor with enhanced heat dissipation by windings. The motor adopts a sandwich structure with a middle stator and two rotors in the axial direction. The motor stator is composed of Q stator tooth units, where Q is the number of slots in the motor, which is a positive integer multiple of the number of motor phases m. Each stator tooth unit includes a stator tooth iron core and a coil wound on the stator tooth iron core, and a superconducting flat heat pipe is arranged between two adjacent stator tooth units. One end of the superconducting flat heat pipe is in close contact with the two stator tooth unit windings sandwiched between it, and the other end is inserted into the cooling channel in the stator support. Utilizing the strong heat transfer and strong heat transfer characteristics of the superconducting flat heat pipe, the heat of the winding is quickly transferred to the cooling runner of the stator support through the superconducting flat heat pipe, so as to achieve enhanced heat dissipation of the winding and increase the torque density of the in-wheel motor.

The patent US7635932B2 discloses an electric machine comprising a ferromagnetic salient pole stator core, windings formed on poles of the stator core, at least one heat pipe at least partially embedded in the stator core where the heat generated during peak excitation of the windings is transferred to the heat pipe. The stator core comprises a plurality of multiple pole core segments, each core segment having embedded with at least one heat pipe, and the heat pipe has a T-shaped configuration comprising a first portion partially embedded in the stator core along the radial direction and a second portion situated outside of the stator core, the first and second portions generally perpendicular to each other. This invention describes various embodiments having heat pipes embedded in the stator core in different configurations.

OBJECT OF THE INVENTION

This section is intended to introduce certain objects of the disclosed methods and systems in a simplified form, and is not intended to identify the key advantages or features of the present disclosure.

The main object of the present invention is to provide a cooling system for brushless motors.

Another object of the present invention is to provide a forced fluid cooling system to remove heat from the stator of outrunner brushless motors.

A further object of the present invention is to provide a heat transfer cooling system to remove heat from the stator of inrunner brushless motors.

It is yet a further object of the present invention to provide heat transfer elements to absorb the heat produced in the stator of outrunner brushless motors.

It is still yet a further object of the present invention to provide heat pipes to cool the heat transfer elements in the stator.

It is still yet a further object of the present invention to provide a coolant to cool the heat pipes in the motor. It is still yet a further object of the present invention to provide a waterproof and dustproof casing for the motor of the present invention.

These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for the purpose of illustration only, one embodiment in accordance with the present invention.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in a simplified format that are further described in the detailed description of the invention. This summary is not intended to identify key or essential inventive concepts of the invention, nor is it intended for determining the scope of the invention.

In order to overcome the heating problems of brushless motors the present invention provides a forced fluid cooling system to remove heat from the stator of the hub motor.

The present invention is an outrunner type brushless DC motor having a stator that is present within a rotor and the stator has a stator core with a plurality of stator teeth. Each of the stator teeth has a plurality of fin slots. The hub motor of the present invention has a cooling system to cool the stator, which includes a radial heat transfer element for absorbing heat from the stator. The radial heat transfer element has a plurality of fins on its outer surface which is fitted in the plurality of fin slots in the stator teeth and by this way the radial heat transfer element is attached to the stator core. The plurality of fins absorbs the heat produced in the stator core. The cooling system of the present invention further consists of a plurality of U shaped heat pipes for removing heat from the radial heat transfer element and the heat pipes are arranged in contact with the radial heat transfer element. The cooling system of the present invention also includes a hollow stator shaft that is placed at the center of the stator. The hollow stator shaft has an inlet and outlet for coolant entry and exit respectively, where the coolant cools one side of the heat pipes. As the coolant flows in the hollow stator shaft the heat from the heat pipes are removed by heat transfer process as the coolant absorbs the heat.

Another motor of the present invention is an inrunner type brushless DC motor which consists of an outer stator and an inner rotor where the stator core has plurality of stator teeth and also a plurality of fin slots are provided in each of the stator teeth on the outer surface of the stator core. The rotor which is arranged within the stator consists of a rotor shaft. The inrunner brushless DC motor of the present invention has a cooling system which includes a heat transfer element, a plurality of U shaped heat pipes and a fan. The heat transfer element has a plurality of fins which are placed within the plurality of fin slots of the stator core such that the stator is present within the heat transfer element. A plurality of slots is provided in the heat transfer element where the plurality of heat pipes is arranged. The fan is located behind the heat pipes and connected to the rotor shaft such that the rotor shaft rotates the fan. The heat transfer element absorbs the heat from the stator core and the heat pipes cool the heat transfer element. The heat pipes are further cooled by the fan which removes the heat from the motor.

In these ways the cooling system of the present invention removes heat from the stator core of outrunner and inrunner brushless DC motors.

To the accomplishment of the foregoing and related ends, certain illustrative aspects of the disclosure are described herein in connection with the following description and the annexed drawing. These aspects are indicative, however, of but a few of the various ways in which the principles of the disclosure can be employed and the subject disclosure is intended to include all such aspects and their equivalents. Other advantages and novel features will become apparent from the following detailed description of the disclosure when considered in conjunction with the drawing.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawing. It is appreciated that this drawing depicts only typical embodiments of the invention and are therefore not to be considered limiting its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWING

In order to better understand the present invention of the brushless motor and their cooling system, the characteristics of object of the present invention, will be better viewed from the detailed description herein after, which is only for a way of example, associated to the drawings referenced below, which are an integral part of this application. The parts in the drawings are not drawn to scale; the main objective is to understand the components, their arrangement and their working.

FIG. 1 is a schematic diagram illustrating the perspective view of the outrunner brushless DC motor of the present invention;

FIG. 2 is a schematic diagram illustrating the cross sectional view of the outrunner brushless DC motor of the present invention;

FIG. 3 is a schematic diagram illustrating the perspective view of the internal assembly of the outrunner brushless DC motor of the present invention; FIG. 4 is a schematic diagram illustrating the perspective view of the stator of the outrunner brushless DC motor of the present invention;

FIG. 5 is a schematic diagram illustrating the exploded perspective view of the internal assembly of the outrunner brushless DC motor of the present invention;

FIG. 6 is a schematic diagram illustrating the exploded perspective view of the cooling system of the outrunner brushless DC motor of the present invention;

FIG. 7 is a schematic diagram illustrating the cross sectional view of the cooling system of the outrunner brushless DC motor of the present invention;

FIG. 8 is a schematic diagram illustrating the perspective view of the inrunner brushless DC motor of the present invention;

FIG. 9 is a schematic diagram illustrating the perspective view of the cooling system of the inrunner brushless DC motor of the present invention;

FIG. 10 is a schematic diagram illustrating the exploded perspective view of the inrunner brushless DC motor of the present invention;

FIG. 11 is a schematic diagram illustrating the cross sectional perspective view of the inrunner brushless DC motor of the present invention;

FIG. 12 is a schematic diagram illustrating another perspective view of the cooling system of the inrunner brushless DC motor of the present invention

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. Furthermore, in terms of the construction of the product, have been represented in the drawings by conventional symbols, and the drawings io may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system and/or method, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Furthermore, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Any headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

The detailed description of the brushless motors and their cooling system; object of the present invention will be made in accordance with the identification of components that form the basis of the figures described above.

After observing the problems in the prior art, the idea of designing a cooling system for brushless DC motors which removes heat from the stator core is disclosed in the present invention detailed description which has a combination of heat transfer element and heat pipes.

For purposes of the present disclosure, the term “Outrunner” refers to brushless motors having an inner stator and an outer rotor where the rotor spins around the stator. For purposes of the present disclosure, the term Inrunner refers to brushless motors having an outer stator and an inner rotor where the rotor spins within the stator.

For purposes of the present disclosure, the term “Heat Transfer Element” refers to any solid material having high thermal conductivity that transfers heat from a hot surface to a cold surface.

For purposes of the present disclosure, the term “Fins” refers to any surfaces that extend from an object to increase the rate of heat transfer from one object to another.

For purposes of the present disclosure, the term “Heat Pipe” refers to a heat-transfer device that combines the principles of both thermal conductivity and phase transition to effectively transfer heat between two solid interfaces.

Referring to the Fig. 1 which shows an outrunner brushless DC motor (1 ) of the present invention, where the outrunner brushless DC motor (1) has an inner stator (2) and an outer rotor (3). The stator (2) consists of a stator core (21 ) and the stator core (21 ) has a plurality of stator teeth (22) extending outwards from the stator core (21 ) as shown in the Fig. 3. Each of the stator teeth (22) is provided with at least two fin slots (23) which extend in the outward direction from the stator core (21 ) in to the stator teeth (22). Fig. 2 shows that the outer rotor (3) is arranged surrounding the inner stator (2) and an air gap is provided between the rotor (3) and the stator (2).

The outrunner brushless DC motor (1 ) of the present invention consists of a cooling system (4) as shown in Fig. 5. The cooling system (4) consists of a radial heat transfer element (41 ) which is made up of a material having high thermal conductivity. The radial heat transfer element (41 ) has a first circular structure (411 ) which has a plurality of fins (413) arranged on its outer surface such that the plurality of fins (413) are extended radially outwards. The radial heat transfer element (41 ) has a second circular structure (412) which has a smaller diameter than the first circular structure (411 ) and the second circular structure (412) is arranged within the first circular structure (411 ). On one side of the radial heat transfer element (41 ) the first circular structure (411 ) and the second circular structure (412) are connected and the other side is open. A gap is formed between first circular structure (411 ) and the second circular structure

(412) which houses a plurality of slots (414) arranged on the inner side of the first circular structure (411 ) and the outer side of the second circular structure (412). The radial heat transfer element (41 ) is fitted in the stator core (21 ) by means of the plurality of fins (413), where the plurality of fins

(413) of the radial heat transfer element (41 ) is inserted into the plurality of fin slots (23) of the stator (2). Fig. 4 shows the arrangement of the plurality of fins (413) within the plurality of the fin slots (23) of the stator teeth (22).

The cooling system (4) further consists of a plurality of U shaped heat pipes (42) to further remove heat from the radial heat transfer element (41 ) which absorbs heat from the stator (2). The heat pipes (42) used in the present invention are flat and U shaped having a condensing side (422) on one side of the U shape and an evaporating side (421 ) on the other side of the U shape. Generally heat pipes are used to remove heat from a particular system of surface, where they have an outer casing, a layer of wick, a vapour cavity and a working fluid. The general working principle of a heat pipe is that the working fluid absorbs heat from the evaporating side and evaporates in to a vapour then it moves towards the condensing side through the vapour cavity. The vapour gets condensed and becomes a fluid and is absorbed by the wick which moves the fluid to the evaporating side for the working cycle to be repeated. The condensing side of the heat pipe may require external cooling means to condense the fluid. In the present invention the plurality of U shaped heat pipes (42) are arranged within the plurality of slots (414) present in the radial heat transfer element (41 ).

Fig. 6 shows the plurality of U shaped heat pipes (42) arranged within the plurality of slots (414) between the first circular structure (411 ) and the second circular structure (412) from the open side of the radial heat transfer element (41 ). The plurality of U shaped heat pipes (42) are arranged such that the evaporating side (421) of the heat pipes (42) are in contact with the first circular structure (411 ) and the condensing side (422) of the heat pipes (42) are in contact with the second circular structure (412) as shown in Fig. 2. The heat pipes (42) remove heat from the radial heat transfer element (41 ) which is absorbed from the stator (2).

The cooling system (4) also has a hollow stator shaft (43) placed at the center of the stator (2) such that the hollow stator shaft (43) is fitted within the second circular structure (412) as shown in Fig. 2. The hollow stator shaft (43) does not rotate and it has an inlet end (431 ) and an outlet end

(432). The outer surface of the hollow stator shaft (43) is in contact with the inner surface of the second circular structure (412). A coolant (433) is passed into the hollow stator shaft (43) from the inlet end (431 ) by means of a pump (436). The coolant (433) cools the condensing side (422) of the heat pipes (42) that are in contact with the second circular structure (412) and flows out of the hollow stator shaft (43) from the outlet end (432). An external condenser (434) is provided (not shown in fig.) to cool the coolant

(433) which is then stored in a reservoir (435) and pumped back into the inlet end (431 ). Fig .7 shows the flow of coolant (433) from the inlet end (431 ) to the outlet end (432) within the hollow stator shaft (43). The outrunner brushless DC motor (1 ) also consists of an outer casing (5) as shown in Fig. 1 which has a hydrophobic mesh integration which permits the entry of air but prevents the entry of water and dust. The cooling system (4) works such that the plurality of fins (413) absorbs heat from the stator teeth (22) which heats the radial heat transfer element (41 ). The heat pipes (42) remove the heat from the radial heat transfer element (41 ) and the flow of coolant (433) is provided in the hollow stator shaft (43) to cool the condensing side (422) of the heat pipes (42) and the coolant (433) coming out of the hollow stator shaft (43) is further cooled externally by condenser (434).

Referring to Fig. 8 which shows an inrunner brushless DC motor (6) of the present invention has an inner rotor (62) and an outer stator (61 ). The outer stator (61 ) consists of a stator core (611 ) having a plurality of stator teeth (612) that extend inwards towards the centre from the stator core (611 ) as shown in Fig. 9. Each of the stator teeth (612) consists of a plurality of fin slots (613) that extend from the outer surface of the stator core (611 ) to the centre within the stator teeth (612). The inner rotor (62) is present within the outer stator (61 ) and the inner rotor (62) has a rotor shaft (621 ). Fig. 10 shows the exploded view of the various components of the inrunner brushless DC motor (6).

The inrunner brushless DC motor (6) also consists of a cooling system (7) which includes a heat transfer element (71 ) that is made up of a material having high thermal conductivity. The heat transfer element (71 ) consists of an outer frame structure (711 ), where the external surface of the outer frame structure (711 ) is shaped according to the external shape of the inrunner brushless DC motor (6). The heat transfer element (7) also has an inner circular structure (712) present within the outer frame structure (711 ), having a plurality of fins (713) on the inner surface of the inner circular structure (712). The outer frame structure (711 ) and the inner circular structure (712) are connected with each other on one side and open on the other side. A plurality of slots (714) is provided in the inner side of the outer frame structure (711 ) and the outer side of the inner circular structure (712). The stator (61 ) is fitted in the heat transfer element (71) such that the plurality of fins (713) is inserted in the plurality of fin slots (613) in the stator teeth (612).

The cooling system (7) of the inrunner brushless DC motor (6) of the present invention also consists of a plurality of U shaped heat pipes (72). The plurality of U shaped heat pipes (72) is arranged in the plurality of slots (714) between the outer frame structure (711 ) and the inner circular structure (712). Fig. 9 shows the stator (61 ) arranged within the heat transfer element (71 ) and the heat pipes (72) arranged between the outer frame structure (711 ) and the inner circular structure (712). The cooling system (7) further consists of a fan (73) which is placed behind the heat transfer element (71 ) and the plurality of heat pipes (72). The centre of the fan (73) is connected to the rotor shaft (621 ) and the fan (73) rotates based on the rotation of the rotor shaft (621 ) as shown in Fig. 11 . The fan (73) removes the heat from the motor (6) and cools the heat pipes (72).

The cooling system (7) of the inrunner brushless DC motor (6) works by initially removing the heat from the stator core (611 ) using the plurality of fins (713), the heat transfer element (71 ) is thus heated so it is then cooled by heat pipes (72). The cooling of heat pipes (72) is done by the fan (73) which removes the hot air within the motor (6). This design of the heat transfer element (71 ) enables to extract heat evenly from the major heat zones of the stator (61 ) which ultimately enables the inrunner brushless DC motor (6) to run continuously for a longer period of time without overheating. Fig. 12 shows the rotor (62) along with the rotor shaft (621 ) arranged within the stator (61 ) and the fan (73) connected to the rotor shaft (621 ).

Claims

We Claim:

1 . A brushless motor consisting of: a inner stator (2), which consists of, a stator core (21 ) having a plurality of stator teeth (22), a plurality of fin slots (23) provided in each of the plurality of stator teeth (22); a outer rotor (3); wherein the inner stator (2) and the outer rotor (3) forms an outrunner brushless DC motor (1 ); an outer stator (61 ), which consists of, a stator core (611 ), having a plurality of stator teeth (612), a plurality of fin slots (613), provided in each of the plurality of stator teeth (612) on the outer surface of the stator core (611 ); an inner rotor (62), which consists of: a rotor shaft (621 ); wherein the outer stator (61 ) and inner rotor (62) forms an inrunner brushless DC motor (6); characterized in that, a cooling system (4) for an outrunner brushless DC motor (1 ) consisting of: a radial heat transfer element (41 ), which consists of: a first circular structure (411 ) having a plurality of fins (413) arranged radially on the outer surface of the first circular structure (411 ), a second circular structure (412) placed within the first circular structure (411 ), the second circular structure (412) having a smaller diameter than the first circular structure (411 ), wherein the first circular structure (411 ) and the second circular structure (412) are connected with each other on one side and open on the other side, wherein a plurality of slots (414) is provided in the inner side of the first circular structure (411 ) and the outer side of the second circular structure (412); a plurality of U shaped heat pipes (42) arranged within the plurality of slots (414), between the first circular structure (411 ) and the second circular structure (412), wherein the evaporating side (421 ) of each of the plurality of heat pipes (42) is in contact with the first circular structure (411 ) and the condensing side (422) of each of the plurality of heat pipes (42) is in contact with the second circular structure (412); a hollow stator shaft (43) placed at the center of the stator (2), consisting of, an inlet end (431 ) on one side, an outlet end (432) on the other side, wherein a coolant (433) is pumped inside the hollow stator shaft (43) which flows from the inlet (431 ) to outlet end (432) while cooling the condensing side (422) of each of the plurality of heat pipes (42) as the outer surface of the hollow stator shaft (43) is in contact with the inner surface of the second circular structure (412) of the radial heat transfer element (41 ); wherein the radial heat transfer element (41 ) is fitted in the stator core (21 ) such that the plurality of fins (413) are placed within the plurality of fin slots (23) of the stator teeth (22); a cooling system (7) for an inrunner brushless DC motor (6) consisting of: a heat transfer element (71 ), which consists of: an outer frame structure (711 ), wherein the external surface of the outer frame structure (711 ) is shaped according to the external shape of the brushless motor (6), an inner circular structure (712), present within the outer frame structure (711 ), having a plurality of fins (713) on the inner surface of the inner circular structure (712), wherein the outer frame structure (711 ) and the inner circular structure (712) are connected with each other on one side and open on the other side, wherein a plurality of slots (714) is provided in the inner side of the outer frame structure (711 ) and the outer side of the inner circular structure (712); a plurality of U shaped heat pipes (72), arranged within the plurality of slots (714), between the outer frame structure (711 ) and the inner circular structure (712); a fan (73), positioned behind the plurality of heat pipes (72) and connected to the rotor shaft (621 ), wherein the rotor shaft (621 ) rotates the fan (73) which provides cooling for the plurality of heat pipes (72); wherein the stator core (611 ) is fitted within the heat transfer element (71 ) such that the plurality of fins (713) are placed within the plurality of fin slots (613), wherein the plurality of fins (713) of the heat transfer element (71 ) absorb heat from the stator core (611 ), where the heat transfer element (71 ) is cooled by the plurality of heat pipes (72) and the plurality of heat pipes (72) are cooled by the fan (73).

2. The brushless motor as claimed in claim 1 , wherein the plurality of fins (413) of the radial heat transfer element (41 ) absorbs heat from the stator core (21 ) of the outrunner brushless DC motor (1 ).

3. The brushless motor as claimed in claim 1 , wherein the radial heat transfer element (41 ) dissipates heat from the stator (2) to the plurality of heat pipes (42) of the outrunner brushless DC motor (1 ).

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4. The brushless motor as claimed in claim 1 , wherein the evaporating side (421 ) of each of the plurality of heat pipes (42) removes heat from the radial heat transfer element (41 ) of the outrunner brushless DC motor (1 ). 5. The brushless motor as claimed in claim 1 , wherein the condensing side (422) of each of the plurality of the heat pipes (42) is cooled by the coolant (433) flowing in the hollow stator shaft (43) of the outrunner brushless DC motor (1 ).

6. The brushless motor as claimed in claim 1 , wherein the coolant (433) coming out of the outlet end (432) of the hollow stator shaft

(43) is condensed and stored in a reservoir (435) and pumped back into the inlet end (431 ) of the outrunner brushless DC motor (1 ).

7. The brushless motor as claimed in claim 1 , wherein the outrunner brushless DC motor (1 ) further consists of an outer casing (5) with hydrophobic mesh integration to prevent the entry of dust and water.

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